Fort Lauderdale , Florida -LRB- CNN -RRB- -- A Florida teenager attacked and set on fire last month , allegedly by five teenage friends , was undergoing skin graft surgery Friday , the first procedure in his recovery , a hospital spokeswoman said .

Michael Brewer , who suffered burns over 65 percent of his body , will have his own skin transplanted onto the burned areas of his back and buttocks , said Lorraine Nelson , a spokeswoman at the University of Miami 's Jackson Memorial Hospital Burn Center .

Brewer will return to the intensive care unit after the surgery . He has been heavily sedated since the October 12 incident and on a ventilator until last week to keep him alive .

He is listed in guarded condition .

On Thursday , three teens accused of setting Brewer on fire pleaded not guilty to charges of attempted murder , a public defender for one of the boys said .

Each of the three -- Denver Jarvis and Matthew Bent , both 15 , and Jesus Mendez , 16 -- is charged as an adult with one count of attempted murder in the second degree in the attack in Deerfield Beach , Florida .

They were arraigned in Broward County Circuit Court before Judge Dale Cohen , and are being held without bond .

Prosecutors say the three boys were in a gang that poured alcohol over Brewer , then set him ablaze in a dispute over $ 40 , a video game and a bicycle .

Gordon Weekes , Bent 's attorney , denounced the fact that the teens were charged as adults .

`` It 's been decided by society that a 15-year-old ca n't vote , ca n't join the armed forces and can not buy alcohol , because society has recognized that children do not have the ability to appreciate the long-term consequences of their actions , '' he said .

`` But they can treat them as adults in court , when we have very capable remedies for them in the juvenile justice system , which is geared towards rehabilitation , '' Weekes added .

The attorney said he and the other two public defenders plan to make separate motions to the court asking that their clients be allowed to post bond .

Detectives say eyewitnesses told them that Mendez used a lighter to set fire to Brewer after Jarvis allegedly poured alcohol over him . They said Bent allegedly encouraged the attack .

Authorities say that Mendez admitted setting Brewer on fire , and that he made a `` bad decision , '' according to an arrest transcript .

Two other boys who were allegedly involved -- a 13-year-old and a 15-year-old -- have been charged as juveniles .

Witnesses say Brewer jumped into the swimming pool at his apartment complex to put out the flames .

Detectives with the Broward County Sheriff 's Office have been unable to interview Brewer .

`` We hope that we can maybe get a statement this week , '' sheriff 's spokesman Jim Leljedal said . `` Detectives have been waiting for him to recover to the point where he 's strong enough to give us a complete statement . ''

Doctors say Brewer is improving but his condition is tenuous because of the severity of his burns and the possibility of infections . Most of his burns are on his back and buttocks ; his face and hands were largely spared , doctors say .

Brewer 's doctor told CNN the teen faces several more months in the hospital , and will need multiple skin grafts and surgeries .

`` They still have to perform several operations on him for skin grafting , but his parents are with him all the time , '' Nelson said .

`` I do n't tell him what happened , '' Brewer 's mother , Valerie , told CNN affiliate WFOR-TV . `` I just tell him he 's in the hospital and he 's safe and he 's getting better .

`` And he 'll say , ` Am I going to be OK ? ' And I say ` Yes , Michael . You 're going to be fine . You 're going to be just fine , ' '' she said .

Investigators believe Brewer owed Bent $ 40 for a video game . When Brewer did not pay , police say , Bent stole Brewer 's father 's bicycle . Brewer reported him to police and Bent was arrested , police say .

The next day , the group surrounded Brewer . According to witnesses , the five boys called Brewer `` a snitch '' and set him on fire .

The Brewer family told WFOR that none of the families of the accused boys have tried to contact them , but that it does n't matter .

`` We ca n't focus on it . They 'll get theirs is all we can say . I do n't focus on it , '' Brewer 's father , also named Michael , told WFOR .

If convicted , each of the three teen suspects could face up to 30 years in prison .

A court-appointed psychologist who has examined two of the five boys allegedly involved in the attack told CNN they are competent to take part in legal proceedings and assist their attorney .

`` I can describe both of them as being afraid , being fearful , '' said Michael Brannon , a forensic psychologist , without identifying the boys . `` I can describe both of them as being tearful at various times during the interview , especially when talking about the specific incident which led to the injuries of the victim . ''

Psychologists are often brought into cases involving teenagers and young adults to judge their mental capabilities to determine their competency to proceed . They must determine whether the alleged attackers understand the charges against them , the court proceedings and potential sentences .

Psychologists also must evaluate whether the defendants can talk about what happened and communicate effectively with defense attorneys .

`` I do n't think they expected to have happened , what happened , '' Brannon said . `` It 's a horrible event that occurred , but this was not their conceptualization , in my opinion , of what was going to happen . ''

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Hospital spokeswoman says Michael Brewer having own skin put onto burned areas

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Brewer , 15 , in guarded condition , will go back to intensive care after procedure

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More surgeries to come ; October 12 attack left burns over 65 percent of his body

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3 of the 5 teens accused of setting Brewer on fire plead not guilty to attempted murder